thunderstick

i have two grounds reading voltage, one is 5+ volts, the other is 10+ volts. one is definitely coming from inside the car, and i suspect the other is, too. but someone expound on this issue cuz i'm thinking there should be no voltage on a ground what-so-ever. so if this is right, then i need to start searching for the culprit(s) that are causing the problem. and btw, the grounds only become "hot" when the key is turned on...

KAM

firebirdjosh

iTrader: (1)

Theres only one ground, check for broken connections to the chassis.

thunderstick

the connections are all good. something somewhere is causing this situation - a sensor or something. could even be the gauge cluster, since it's on the same ground system. not all systems are reading a voltage, so if there was only one ground, then everything would have voltage, i would think.

Trickster

Hello Thunderstick,

By looking at those schematics of the grounds that I sent you, which one has the voltage to it?

thunderstick

sorry for the delayed reply... i'm at my "remote" location with no internet access in the evening.

one of the "hot" grounds is the one coming thru pin "F8" and if i recall, that is the one getting 10+. the other is coming thru pin "C7", and that is getting 5+. that voltage is present with the ecm, fp relay, and the ac press switch all disconnected. both of these grounds connect at G112, and these two were coupled together. (they are separated at the moment) the other coupled grounds are the O2 (tan) and D1, i believe. (i don't have them in front of me), but they are apparently getting "0" volts. now if i couple all of those grounds back together, the volts at G112 go down to like .05V, but the fuel pump cycle with the lights is still there.

firebirdjosh

iTrader: (1)

If you are touching a ground, you are connected to the negative side of the battery. There CANNOT be different voltages on the same connection. If one ground is reading 5V and the other is 10V then they are not connected and they are definitely not grounded.

thunderstick

and that's the pisser here, cuz, apparently the fault is inside somewhere. i've been over and over and back over everything i did, and cannot find a disconnected ground. the harness stayed in the car during the rebuild and i was very careful whenever i moved it. everything works, nothing shorts or blows fuses. the different voltages make no sense, either. i hear what you're saying about them not being connected and definitely not being grounded, but i cannot figure out where.

the only other two grounds that weren't on the schematics trickster sent me were to the cooling fans (which hook up at the same location as the pigtail off the neg batt cable, and another small 2-wire one that is attached at the firewall by the relays on the driver's side... but they are in the same place as they were before, so...

91Z28-350

Isn't this the same problem you've been looking at for about a month? Damn...that's a long time.

See if you can trace the wire back to the chassis. It sounds like some wires may be broken, that or it isn't getting grounded. This may happen if the chassis ground isn't going metal to metal or the ring terminal is broken off from the wire, but still within the sleeve.

Are your grounds using metal screws? If they aren't you may have to scrape the paint to get a metal to metal connection to ground.

Unfortunately, you may have to open up the harness if everything else checks out...that sucks, I know However, you can get rid of all the electrical tape and use TechFlex (FlexoWrap, DuraWrap) later, which is a bonus. The electrical tape is annoying and when it comes off it's sticky and gooey.

thunderstick

yea, this is the same damn issue... but i only can work on it on weekends, so time is limited. regardless, i still can't determine what the problem is, but on the other side of the coin, i don't want to have to pay a lot of $ for a shop to find and fix, either. may have to do that, though. i've already got half the harness open up anyways, so a little more certainly ain't a big deal. i just don't understand how supposedly everything can be grounded and get a hot wire. i think that ground going thru F8 and C7 should be going IN to the car to those components, not reading hot on the back side.

91Z28-350

F8 and C7? Are those pins on the ECU harness or are you referring to something else?

I think the point we are making is that it may not be grounded. Ground is relative, so there will be a nominal voltage differential between chassis grounds. It's all relative to the negative battery terminal, add resistance for the sheetmetal and another ground point say 6 feet away, and you'll get a small differential. Nothing large in magnitude like 5V or 12V though. That large a differential may indeed indicate that the wire isn't grounded. That would be my guess anyway. I'm not sure it is a short, as fuses would likely blow and wires may burn up. I'm thinking it's just a misconnection. I'd start there, checking the terminals and the condition of the wire. Can you probe continuity on the wire itself from those pins to the other end of the wire?

I wouldn't pay a shop for it either. It'll be thousands of dollars before they find the problem. Electrical problems are the worst.

thunderstick

those pins are in the C100 connector. both are grounds, going from the head TO the inside of the car. i was just reading a post by sonix that had a similar problem with his ctsy lights, and if i understood it correctly, it was caused by a fuse that looked good, but didn't function good... it seems odd that the problem is originating from inside the car when nothing in there was ever disturbed, so a faulty fuse? maybe... i guess i'll replace every one with a fresh one and other than that, open up every inch of harness that i had open when i did the rebuild and inspect every wire and terminal - and clean (again) every single grounding point whether i disturbed it or not.